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Simplify Fluid Caching #9946

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Simplify Fluid Caching #9946

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c74483f
Simplify glycol specific-heat caching
amirroth Apr 6, 2023
bc1bc3c
Well that was stupid
amirroth Apr 7, 2023
b7d7131
Take 3, reducing precision bits
amirroth Apr 7, 2023
fb0905b
Take 4: a quick performance test
amirroth Apr 8, 2023
25fc1f7
Merge remote-tracking branch 'origin/develop' into SimplifyFluidCaching
amirroth Apr 8, 2023
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45 changes: 36 additions & 9 deletions src/EnergyPlus/FluidProperties.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -7463,26 +7463,53 @@ namespace FluidProperties {
std::string_view const CalledFrom // routine this function was called from (error messages)
)
{
std::uint64_t constexpr Grid_Shift = 64 - 12 - t_sh_precision_bits;
// Get the input if we haven't already
if (state.dataFluidProps->GetInput) {
GetFluidPropertiesData(state);
state.dataFluidProps->GetInput = false;
}

// If no glycols, no fluid properties can be evaluated
int GlycolNum(0);
if (state.dataFluidProps->NumOfGlycols == 0)
ReportFatalGlycolErrors(
state, state.dataFluidProps->NumOfGlycols, GlycolNum, true, Glycol, "GetSpecificHeatGlycol", "specific heat", CalledFrom);

// If glycol index has not yet been found for this fluid, find its value now
if (GlycolIndex > 0) {
GlycolNum = GlycolIndex;
} else { // Find which glycol (index) is being requested
GlycolNum = FindGlycol(state, Glycol);
if (GlycolNum == 0) {
ReportFatalGlycolErrors(
state, state.dataFluidProps->NumOfGlycols, GlycolNum, true, Glycol, "GetSpecificHeatGlycol", "specific heat", CalledFrom);
}
GlycolIndex = GlycolNum;
}

int constexpr SpecificHeatPrecisionBits = 16;
std::uint64_t constexpr SpecificHeatMask = (FluidPropsGlycolData::SpecificHeatCacheSize - 1);
std::uint64_t constexpr SpecificHeatShift = 64 - 12 - SpecificHeatPrecisionBits;

double const t(Temperature + 1000 * GlycolIndex);
double const t = Temperature;

DISABLE_WARNING_PUSH
DISABLE_WARNING_STRICT_ALIASING
DISABLE_WARNING_UNINITIALIZED
// cppcheck-suppress invalidPointerCast
std::uint64_t const T_tag(*reinterpret_cast<std::uint64_t const *>(&t) >> Grid_Shift);
std::uint64_t const tagTemp = *reinterpret_cast<std::uint64_t const *>(&t) >> SpecificHeatShift;
DISABLE_WARNING_POP

std::uint64_t const hash(T_tag & t_sh_cache_mask);
auto &cTsh(state.dataFluidProps->cached_t_sh[hash]);
std::uint64_t const hash = tagTemp & SpecificHeatMask;
auto &glycol = state.dataFluidProps->GlycolData(GlycolIndex);
auto &cacheEntry = glycol.specificHeatCache[hash];

if (cTsh.iT != T_tag) {
cTsh.iT = T_tag;
cTsh.sh = GetSpecificHeatGlycol_raw(state, Glycol, Temperature, GlycolIndex, CalledFrom);
if (cacheEntry.tagTemp != tagTemp) {
cacheEntry.tagTemp = tagTemp;
cacheEntry.specificHeat = GetSpecificHeatGlycol_raw(state, Glycol, Temperature, GlycolIndex, CalledFrom);
}

return cTsh.sh; // saturation pressure {Pascals}
return cacheEntry.specificHeat; // saturation pressure {Pascals}
}

Real64 GetSpecificHeatGlycol_raw(EnergyPlusData &state,
Expand Down
33 changes: 12 additions & 21 deletions src/EnergyPlus/FluidProperties.hh
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Original file line number Diff line number Diff line change
Expand Up @@ -93,12 +93,6 @@ namespace FluidProperties {
constexpr static std::string_view EthyleneGlycol("EthyleneGlycol");
constexpr static std::string_view PropyleneGlycol("PropyleneGlycol");

#ifdef EP_cache_GlycolSpecificHeat
int constexpr t_sh_cache_size = 1024 * 1024;
int constexpr t_sh_precision_bits = 24;
std::uint64_t constexpr t_sh_cache_mask = (t_sh_cache_size - 1);
#endif

struct FluidPropsRefrigerantData
{
// Members
Expand Down Expand Up @@ -249,6 +243,15 @@ namespace FluidProperties {
Array1D<Real64> ViscTemps; // Temperatures for viscosity of glycol
Array1D<Real64> ViscValues; // viscosity values (mPa-s)

#ifdef EP_cache_GlycolSpecificHeat
struct SpecificHeatCacheEntry {
std::uint64_t tagTemp = 0; // 0x8000000000000000 Initialize with something that is not a valid tag
Real64 specificHeat = 0.0;
};

static int constexpr SpecificHeatCacheSize = 1024;
std::array<SpecificHeatCacheEntry, SpecificHeatCacheSize> specificHeatCache;
#endif
// Default Constructor
FluidPropsGlycolData()
: GlycolIndex(0), Concentration(1.0), CpDataPresent(false), CpLowTempValue(0.0), CpHighTempValue(0.0), CpLowTempIndex(0),
Expand All @@ -257,6 +260,9 @@ namespace FluidProperties {
CondLowTempIndex(0), CondHighTempIndex(0), ViscDataPresent(false), NumViscTempPts(0), ViscLowTempValue(0.0), ViscHighTempValue(0.0),
ViscLowTempIndex(0), ViscHighTempIndex(0)
{
#ifdef EP_cache_GlycolSpecificHeat
specificHeatCache[0].tagTemp = 0x8000000000000000; // 0 is a valid tag for entry 0, so need to initialize with something else;
#endif
}
};

Expand Down Expand Up @@ -332,18 +338,6 @@ namespace FluidProperties {
}
};

struct cached_tsh
{
// Members
std::uint64_t iT;
Real64 sh;

// Default Constructor
cached_tsh() : iT(1000), sh(0.0)
{
}
};

void InitializeGlycRoutines();

void GetFluidPropertiesData(EnergyPlusData &state);
Expand Down Expand Up @@ -658,9 +652,6 @@ struct FluidPropertiesData : BaseGlobalStruct
int TempRangeErrCountGetInterpolatedSatProp = 0;
int TempRangeErrIndexGetInterpolatedSatProp = 0;

#ifdef EP_cache_GlycolSpecificHeat
std::array<FluidProperties::cached_tsh, FluidProperties::t_sh_cache_size> cached_t_sh;
#endif

void clear_state() override
{
Expand Down